package demo;

// 2、无头双向链表实现
public class MyLinkedList implements MyList{

    static class ListNode{
        public ListNode next;
        public ListNode prev;
        int val;

        public ListNode(int val) {
            this.val = val;
        }
    }
    ListNode head;
    ListNode last;


    //头插法
    public void addFirst(int data){

        ListNode node = new ListNode(data);
        if(head == null){
            head = last = node;
            return;
        }
        head.prev = node;
        node.next = head;
        head = node;
    }
    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if(last == null){
            last = head = node;
            return;
        }
        node.prev = last;
        last.next = node;
        last = node;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        ListNode cur = head;
        ListNode node = new ListNode(data);
        if(index == 0){
            node.next = head;
            head.prev = node;
            head = node;
            return;
        }
        if(index == size()){
            node.prev = last;
            last.next = node;
            last = node;
            return;
        }
        while(index != 0){
            cur = cur.next;
            index--;
        }
        node.next = cur;
        node.prev = cur.prev;
        cur.prev.next = node;
        cur.prev = node;


    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                //开始删除
                if(cur == head) {
                    head = head.next;
                    if(head != null) {
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null) {
                        last = last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
                return;
            }
            cur = cur.next;
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                //开始删除
                if(cur == head) {
                    head = head.next;
                    if(head != null) {
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null) {
                        last = last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }
    //得到单链表的长度
    public int size(){
        ListNode cur = head;
        int count = 0;
        while(cur != null){
            count++;
            cur = cur.next;
        }
        return count;
    }
    public void display(){
        ListNode cur = head;
        while(cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
    public void clear(){
        last = null;
        head = null;
    }
}
